Optical discs and other optical information recording media are becoming popular as information recording media. These optical information recording media include recordable CDs (CD-Rs), each constituted by a light-transmissive resin substrate of 1.2 mm in thickness and 120 mm or 80 mm in diameter on which a reflective layer and recording layer are formed successively. With these optical recording media, data is recorded by forming recording marks via irradiation of a recording laser beam onto the recording layer. In recent years, the market is demanding higher information recording densities. To meet this demand, methods that use a short laser wavelength and an object lens having high numerical apertures (NAs) are considered, and new optical information recording media such as recordable DVDs (DVD±Rs) have developed accordingly. Such DVDs (DVD±Rs) are structured in such a way that two light-transmissive resin substrates of 0.6 mm in thickness are laminated together by sandwiching a reflective layer and recording layer in between, in order to increase the permissible tilt angle of the disc to accommodate its shorter wavelength and higher NA.
In recent years, however, even higher information recording densities are required to record high-definition image data. Accordingly, new optical information recording media have been developed, such as the recordable Blu-ray Disc (BD-R; “Blu-ray Disc” is a registered trademark), that are structured in such a way that a reflective layer and recording layer are formed on the side of a 1.1-mm thick resin substrate where light enters, after which a light-transmissive cover layer of 0.1 mm in thickness is formed on top of the aforementioned side where the reflective and recording layers have been formed. With these optical information recording media, serial numbers, lot numbers and other management information are recorded on individual discs in the form of a barcode for the purpose of manufacturing/storage or distribution/sales management, and used as a means to identify whether or not a given optical disc is by its legitimate manufacturer or distributor. To be specific, a burst cutting area (hereinafter referred to as “BCA”) provided on the innermost side of the area of the optical disc where the recording layer is formed is recorded with a barcode-shaped mark (hereinafter referred to as “BCA mark”), and this BCA mark is read by the optical head of a drive designed to play back optical discs. In addition, a part of this BCA mark is used to prevent illegal copying of information. Accordingly, the BCA mark is becoming increasingly important in the domain of optical discs. As described in Japanese Patent Laid-open No. 2007-335061 or Japanese Patent Laid-open No. 2008-117470, a BCA mark is formed in the BCA by melting and removing the reflective layer via laser beam irradiation. The same is true with BD-ROMs, BD-Rs whose recording layer uses an inorganic material, and BD-Rs whose recording layer uses an organic dye.